Mobile, truck mounted industrial vacuum loaders and cleaners typically include a vacuum body and a vacuum pump coupled to an outlet of the body. One or more inlets are provided to the body and a hose is coupled to the inlets so that a high velocity stream of air may be drawn through the hose to permit loading of material into the body.
It is also common with such equipment to provide a bag house filter between the body and the vacuum pump for filtering the air before it reaches the pump and to prevent damage to the pump, a problem which is especially severe with the expensive positive displacement vacuum pumps being used in modern industrial vacuum loaders and cleaners.
One type of such machines also includes a by-pass feature which permits all or a portion of the filter bags to be bypassed if the machine is being used to load liquids. This necessitates at least two flow paths between the body and the pump, and in most cases two outlets from the body. In this type of modern equipment, the filter bag house includes two sets of in-line filter bags, the by-pass arrangement allowing air, and any entrained debris leaving a first one of the body outlets to be filtered in series through both sets of filters before reaching the pump. This operating mode is typically used when solids are being loaded into the body and where the greatest amount of dust is encountered. In another operating mode, air leaves a second body outlet and is filtered through only a portion of the filter bags before reaching the pump. This mode is used when liquids are being loaded into the body and where fine dust filtration is not necessary.
The changeover from solid to liquid operating modes for such equipment is typically done by manually opening and closing doors inside the body to prevent air from leaving the body other than through the desired exit port. Doors pivotally hinged adjacent the port openings are the most common arrangement, and the operator swings the doors into and out of position and latches the doors in the desired configuration. The changeover is time consuming and requires the machine operator to enter the collection body. It has been suggested that the desired changeover could be accomplished by doors which are moved from outside the body, for example from the top of the body. These suggestions do not overcome all the problems with present designs because the changeover is still time consuming and requires the operator to climb to the top of the body.
Another feature of modern industrial vacuum loading and cleaning equipment is a system for automatically closing a body exit port when liquids are being collected and the liquid reaches a predetermined level. In the type of machine referred to above, the overfilling system includes a float mounted in the body and a connecting element joining the float to a door. When the liquid in the body reaches a certain level, the float is raised through its own buoyancy and, as filling continues, the connecting element pushes the door toward its closed position. Due to the vacuum air flow being drawn through that exit port, when the door approaches sealing engagement, it will be tightly closed by the vacuum and will remain closed until the vacuum is turned off.
In practice it has been noted that the float mechanism, under some conditions, can foul. If the machine operator is not careful, overfilling can then result leading to costly damage to the filter bags and, even more importantly, to the vacuum pump. The solution to this problem is complicated by the interrelationship of the float overfill protection system with the normal liquid-solid changeover procedures.
For purposes of reference, a typical industrial vacuum loader and cleaner with which the present invention is concerned is described in detail in commonly assigned U.S. Pat. No. 3,885,932 issued May 27, 1975, to Lionel G. Moore, Jr. and Thomas P. Flynn and entitled "Dust Filtration System."
Another variety of cleaning machine with which apparatus of the present invention may be used is the pneumatic sewer cleaning equipment. In this type of equipment, a vacuum collection body is also provided, as is a vacuum pump (such as a positive displacement vacuum pump). One or more inlets are provided to the body and an outlet opening of the body is coupled to the vacuum pump so that a high velocity air stream may be drawn through the body. Such machines also typically include a water tank and a hose for injecting water under pressure from the tank into a sewer lateral for flushing debris into a catch basin. Another hose is coupled to the body inlet and lowered into the sewer catch basin. The high velocity air stream drawn though the latter hose pneumatically conveys water and entrained debris into the body. As was the case with industrial vacuum loaders and cleaners, overfilling protection is required for this type of machine. One method in use today comprises providing a liquid level sensor in the body, the sensor being designed for emitting a signal when the liquid level in the body reaches a predetermined level. The sensor is coupled to a vent door to the body located above the predetermined level. The door normally closes a vent opening into the body, but upon receiving a signal, the door is opened to allow air to enter the body. The size of the vent hole is selected so that the vacuum in the body will be reduced to thereby reduce the air velocity in the inlet hose and thus prohibit continued loading. Other systems are known for preventing overfilling, such as the float-door closing system previously discussed for the liquid operating mode of the industrial vacuum loading and cleaning machine.
For purposes of illustration, one type of sewer cleaning machine with which the present invention is concerned is disclosed in a commonly assigned, copending application Ser. No. 828,631, filed Aug. 29, 1977 for "Sewer and Catch Basin Cleaner."
The overfill protection system used with these types of machines also suffer from various drawbacks. For example, the vent door may foul from weathering or from deterioration caused by some materials, and in the event of such failure, the vacuum pump can be damaged, leading to expensive repair or replacement.
A system for positively opening and closing ports to a vacuum body which overcomes the aforementioned problems would be a significant advance in this technology.